The present invention relates to a digitizer tablet with a two-dimensional lighting function and a liquid crystal display device utilizing such tablet.
Digitizer tablets are generally classified by their detection methods into the resistance detection method, the electrostatic capacity method, and the electromagnetic induction method, etc., but structurally, they are generally made of a transparent substrate having one or more transparent electrodes. Normally used for the transparent substrate are glass plates or PET (polyethylene terephthalate), and ITO or tin oxide is used for the transparent electrode. The transparent electrode may be used uniformly over the whole surface, but also in a patterned form. In order to improve the writing feel and to prevent glare effects, the pen Input face is structured to have a plastic film pasted thereon or to provide a fine jog on its surface. Digitizer tablets are used not only as an input device alone but also as a device which can be combined with a CRT or LCD and operate information via a display screen.
Among the prior art, an illuminating device to be arranged in front of a liquid crystal display device is known from Patent Laid-Open Hei 6(1994)-324331. According to the device with the structure proposed therein, illumination can be obtained which is suitable for use with the reflective liquid crystal display mode used widely with various portable equipment.
However, as digitizer tablets with conventional structure have a transparent substrate with one or more transparent electrodes, although there may have been almost no attenuation of the quantity of light inside the transparent substrate, 10% or more of the quantity of light was lost particularly due to surface reflection at the interface between the, transparent electrode and air, thereby becoming dark. Another problem was that as the panel was difficult to look at due to surface reflection, this was especially an issue in the combined use with a display component. Moreover, when pasting an anti-glare film or providing a fine jog on the surface as glare-proof measures, the quantity of light was reduced by another 10% to 20% of the total light transmission, and the contrast effect was reduced due to the irregular reflection on the surface, thereby reducing the picture quality of the display.
The present invention aims at resolving these-problems of the prior art by providing a cost-effective, sample structure of an easy to see, bright digitizer tablet with a two-dimensional illuminating function, and a liquid crystal display device including a digitizer tablet which is especially suitable for use with reflective liquid crystal display modes.